Piezo crystal unit assembly



April 1947- s. s. WACHTMAN 2,418,491

PIEZO CRYSTAL UNIT ASSEMBLY Filed June 5, 1945 2 Sheets-Sheet 1 PatentedApr. 8, 1947 UNITED STATES PATENT OFFICE 9 Claims. 1

My invention relates broadly to piezo electric crystal apparatus andmore particularly to an improved construction of piezo crystal unitassembly.

One of the objects of my invention is to provide a construction of piezoelectric crystal unit assembly which is relatively inexpensive for massproduction and which has a high electrical e'fllciency.

Another object of my invention is to provide an improved construction ofpiezo electriccrystal unit assembly having a minimum number or parts andlow electrical capacity for efllcient operation in piezo electriccrystal control and oscillator circuits.

Still another object of my invention is to provide a construction ofpiezo electric crystal unit assembly which is extremely small in sizeand which may be readily detachably mounted inua circuit terminalassembly of low cost.

Still another object of my invention is to provide a construction ofrelatively flat holder for a piezo electric crystal of a depth which isonly slightly greater than the thickness of the electrode and crystalassembly and yet which provides adequate electrical insulation andmechanical resiliency for the 'mounting of a piezo electric crystalelement for normal vibration in its course of operation in an electricalcircuit.

Other and further objects of my invention reside in the improvedconstruction of a low cost mounting for a piezo electric crystal as setforth more fully in the specification hereinafter following by referenceto the accompanying drawings, in which:

Figure 1 is a view illustrating the piezo electric crystal unit assemblyor my invention about to be placed in the circuit terminal device orholder; Fig. 2 is a front elevatlonal view of the piezo electric crystalunit assembly of my invention; Fig. 3 is a side elevational view of thepiezo electric crystal unit assembly; Fig. 4 is a vertical sectionalview through the piezo electric crystal unit assembly taken on line 4-4of Fig. 2; Fig. 5 is a unit assembly the parts of which are shown inFig.

7; Fig. 9 is a vertical sectional view of the structure of Fig. 8 takensubstantially on line 9-9 of Fig. 8; Fig. 10 is an enlarged verticalsectional 2 view through the piezo electric crystal unit assembly takensubstantially on line Ill-ill of Fig. 8, the view being enlarged inorder to more clearly illustrate the coaction of the several parts; Fig.11 is a front elevational view of the piezo electric crystal unitassembly of my invention mounted in the circuit terminal assembly; Fig.12 is a side elevational view 01' the piezo electric crystal apparatusof my invention with certain parts broken away to more clearlyillustrate the manner of detachably mounting the piezo electric crystalunit assembly in the circuit terminal assembly of my invention; Fig. 13is a, top plan view of the piezo electric crystal apparatus of myinvention partially broken away to show the piezo crystal unit assemblydetachably'mounted in position in the circuit terminal assembly; Fig. 14is a side elevational view of the circuit terminal assembly employedforlmounting the piezo electric crystal unit oi. my invention; and Fig.15 is a top plan viewof the electric circuit terminal assemblyillustrated in Fig. 14.

With the allocation of many additional frequencies in the frequencyspectrum for various services in which the public interest is paramount,the matter of controlling the frequency of operation of signallingcircuits'has assumed enormous proportions. The construction of frequencycontrol apparatus on a mass production scale at low cost is importantfor the adequate development of the art. The piezo electric crystal unitassembly of my invention has been developed with a view of meetingrequirements of the art from the viewpoint of quantity production at lowcost. I provide a shell-like container into which a spring device may beinserted as a resilient support for the electrode and piezo electricplate assembly of the piezo electric crystal unit. The piezo electricplate assembly is arranged with respect to the electrodes to permit freevibration thereof. The spring device serves both as a centering meansfor one of the electrodes as well as to provide a yieldable support forthe electrode assembly. A retaining ring of insulation material embracesthe other of the electrodes and serves as a centering means thereforwithin the enclosing shell. The enclosing shell is rolled to a positionengaging the retaining ring thereby completing the piezo elec tric unitassembly. An inexpensive and compact form of spring clip holder isprovided for detachably mounting the piezo electric crystal unitassembly.

The assembly may be manufactured either in the form of a rectangularshell-like encased unit or as a circular shell-like encased unit. I have3 found the construction highly practical for inexpensive massproduction and as having low electrical capacity and a high degree ofelectrical efficiency.

Referring to the drawings in detail Figure 1 shows one form of piezoelectric crystal unit assembly designated by reference character i aboutto be inserted or removed from the cuplike support designated at 2 asmounted upon supporting base 3. The piezo electric crystal unit assemblyI comprises the shell-like metallic cup 4 in which there is inserted thering-like spring member 5. The ring-like spring member 5 is sinusoidallyshaped about its periphery and has an external diameter whichsubstantially conforms with the internal diameter of the sheetlike cup4. The ring-like spring member 5 thus serves as a centering means forthe circular electrode 6. Electrode 6 has a central projection 'ithereon which has an external diameter conforming with the internaldiameter of the ringlike spring member 5 so that the ring-like springmember 5 fits over the projection l of the electrode 6 sufliciently tocenter the electrode 6 within the shell-like cup I. The electrode 6 iscentrally recessed on its opposite face as represented at 8 leaving theperipheral armular land portion 9 which provides a mechanical supportand an electrical contact for the corners of the piezo electric platerepresented at in.

The opposite electrode of the piezo electric crystal unit assembly isshown at ii as having a recessed central portion i 2 and an annularperipheral portion H. The annular peripheral portion It serves tomechanically and electrically engage the corners of the opposite face ofthe piezo electric crystal plate in. The opposite side of the electrodeii has central projection i5 thereon which extends into the internaldiametrical portion of the retaining ring i6 and serves as an electricalterminal. Retaining ring i6 is formed from insulation material and isprovided with a circular recess I! in one side thereof terminating in anannular shoulder i8 which receives and forms a seat for the circularperipheral portion of the circular electrode ii.

, The circular recess I! in retaining ring i6 is of suificient depth anddiameter to receive the circular electrodes ii and 8 in loose fillingrelation and allow vibratory movement thereof. The retaining ring l6 hasan external diameter. substantially conforming with the internaldiameter of the cup or shell-like metallic casing l for therebycentering electrodes i i and 6 within the casing. Thus electrode 6 iscentered by its entry into circular recess il in retaining ring i6against ring-like spring member 5 while electrode ii is centered whollywithin recess i i of retaining ring i6 for thereby assembling theelectrodes with respect to the piezo electric plate i0 in stackedarrangement within the shell-like container 4 under the yieldablecontrol of ring-like spring member 5. Electrical connection is completedfrom electrode 6 to metallic casing 4 through spring 5. The assemblythus described is maintained in position by rolling over the extremityof the skirt of the shell-like casing l as represented at Ill. Therolled over extremity i9 presents a circular edge 20 thereof incontacting relation to the retaining ring i6 of insulation material formaintaining the piezo electric crystal unit in assembled relation. Thedepth of the shell-like container 4 only slightly exceeds the combinedeifective thickness of the assembly constituted by retaining ring I,electrodes 8 and H,

considered in conjunction with the thickness of the piezo electric platei0 and the effective depth of ring-like spring member 5. Thus the piezoelectric crystal unit assembly is free to vibrate in the generation ofpiezo electric current at maximum efficiency.

In Figs. 1-6 I have explained my invention as directed particularly to acircular construction of piezo electric crystal unit assembly. Certainmass production procedures may be carried out more expeditiously with arectangular or square construction of piezo electric crystal unitassembly. Figs. 7-10 illustrate my invention as applied to a rectangularor square type of piezo electric crystal unit assembly. In thisarrangement the metallic container or shell is pressed from sheet-likematerial to form a substantially square container represented at 2|which receives the spring-like device 22 of peripheral outlinesubstantially conforming with the internal shape of the sheet-likecontainer 2|, the springlike device being of sinusoidal shape forpresenting one bearing surface directly against the end wall of thecontainer 2i and the alternating bearing surface against the peripheryof the electrode represented at 2!. The electrode 23 has a peripheralcontour corresponding in shape to the internal shape of container 2iwith a central projection 24 thereon extending through the interior ofthe rectangularly shaped strip-like member constituting the spring-likedevice 22. Electrode 23 is centered within the sheet-like container 2iby its loose fitting entry into the recess 32 in rectangular retainingring 3i. Electrode 23 is provided with lands at each of the cornersthereof shown at 26 projecting from the central portion represented at25 and providing supports for the corners of the piezo electric plateIll. The fact that the piezo electric plate is contacted at the cornersonly by electrode 23 insures free vibration of the crystal throughoutits area.

The opposite electrode 21 ha lands 2! at the opposite corners thereofprojecting from the central circular portion 28 thereof to establishmechanical and electrical contact with the corners of the opposite faceof piezo electric plate ID. A central projection 30 of circular shapeextends from the opposite side of electrode 21 as shown. A rectangularor square retaining ring of insulation material shown at ll serves tomount the electrodes 21 and 23 in position with respect to shell 2| ininsulated spaced relation thereto. Retaining ring ll of insulationmaterial has a recess 32 formed therein conforming in contour to theperipheral shape of electrodes 21 and 23 whereby electrode 21 may beseated against shoulder 23 of retaining rin 3i with the central portion30 thereof partially projecting through the circular aperture 34 in theopposite face of retaining ring 3|. The dimensions of retaining ring iiare such that retaining ring 2i substantially conforms to the interiorcross section of container 2i thereby centering electrodes 21 and 23within the unit assembly and in coaction with spring member 22 centeringthe unit assembly with respect to the interior walls of the container2i. The

length of the skirt or wall of container 2| is' such that the peripheralextremity of the skirt or wall 2| may be rolled over as represented at35 for retaining the piezoelectric crystal unit assembly in positionwithin the shell-like container 2!. The depth of the container 2i issuch that when the peripheral extremity is rolled over as represented at35 the combined thickness of retaining ring 3|, electrodes 2'! and 28and piezo electric crystal, III in association with spring member 22allows free vibration of the piezo electric crystal within thecontainer.

The circuit term nal assembly for mounting the piezo crystal unitassembly I comprises cup-like support 2 in the form of a bracket havinga central portion 38 mounted upon supporting base 3 and a pair of sideportions 31 and 38 which are shaped to conform with the contour of thepiezo electric crystal unit assembly I. a The side portions 3! and 38have inwardly directed planelike portions 31a and 38a which serve asabutments against which the piezo electric crystal unit assembly I maybe centered and maintained as shown. The portion 36 of the bracketserves as a mounting means for the block 39 of insulation material whichis secured thereto in any suitable manner such as by means of screws 38aand 36b. The upper portion of the block 39 of insulation material isgrooved at "a and into this groove the resilient strip-like member IIIis secured by means of screw 40a. Resilient striplike member 40 has acontacting portion 40b directed inwardly through the open end of thebutton or disc-like piezo crystal unit assembly for establishingconnection with the projecting face l5 of the electrode ll. Strip-likemember 40 tends to continuously urge the piezo electric crystal unitinto supporting relation with the abutment portions 31 and 38 01' thecup-like support 2. The resiliency of the strlp-like member 40 is suchthat the button or disc-like piezo crystal unitv assembly may be readilyinserted or removed from the support for facilitating the change of theassociated electrical circuit from one frequency to another. Theelectric circuit connections are made to the terminal assembly throughconductors, one of which I have indicated at H connected to one of thesecuring screws 36c and the other of which I have shown connected at 42as connected to a lug 40c struck from the resilient strip-like member40. The mannerof supporting the square or rectangular shape or piezoelectric crystal unit of Figs. 7-10 is the same as the method ofmounting the circular piezo electric unit assembly of Figs. 1-6 exceptthat the cup-like support 2 has the abutment portions thereofdifferently shaped to conform with the shape of the containerconstituting the iezo crystal unit assembly.

I have found the embodiments of my invention herein highly practical inconstruction for mass production at low cost, but I realize thatmodifications in detail may be made and I desire that it be understoodthat no limitations upon my invention are intended other than may beimposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United Statesis as follows:

1. A piezo electric crystal unit assembly comprising a metallicshell-like container, a spring member mounted in said container, anelectrode supported by said spring member. a piezo electric crystalplate establishing surface contact with member.

2. A piezo electric crystal unit assembly comprising a metallicshell-like container, a strip-like yieldable member substantiallyconforming in shape with the interior contour or said shell-likecontainer, an electrode supported by said strip like yieldable member, apiezo electric crystal plate having one of its surfaces establishsurface connection with said electrode, a second electrode establishingconnection with the other surface of said piezo electric crystal plate,a, retaining ring of insulation material engaging said last mentionedelectrode and a confining connection between the peripheral edge of saidshell-like container and said retaining ring.

3. A piezo electric crystal unit assembly comprising a shell-likemetallic container, a relatively flat strip-like spring member disposedagainst the end wall of said shell-like container, an electrodesupported by said strip-like spring member,

electrode within said shell-like container and a binding connectionbetween said retaining ring and the peripheral edge of said shell-likecontainer.

4-. A piezoelectric crystal unit assembly comprising a pair of parallelextending electrodes each being recessed centrally of the face thereofproviding peripheral lands thereon, a piezo electric crystal platemounted between the lands of said electrodes and free to vibrate in therecesses provided in said electrodes, a shell-like metallic casing,means for yieldably supporting one of said electrodes with respect tothe interior end wall of said shell-like metallic casing, a retainingring of insulation material peripherally embracing the other of saidelectrodes and a peripheral connection between said retaining ring andthe opposite end or said shell-like container.

5. A piezo electric crystal unit assembly comprising a pair of parallelextending electrodes each being recessed centrally of the face thereofproviding peripheral lands thereon, a piezo electric crytsal platemounted between the lands of said electrodes and free to vibrate in therecesses provided in said electrodes, a shell-like metallic casing, astrip-like spring member disposed in substantially co-planar relation tothe interior I- end wall of said container and one of said electrodes,said strip-dike spring member being sinusoidally shaped with theopposite alternate faces contacting the internal end wall of saidshell-like container and said first mentioned electrode for resilientlyspacing said electrode from the interior end wall of said container, aretaining ring of insulation material peripherally embracing the otherof said electrodes and a Deripheral connection between said retainingring and the opposite end of said shell-like container.

6. A piezo electric crystal apparatus comprising in combination abracket member having a pair of arms with laterally disposed abutmentsthereon, a disc-like piezo crystal unit assembly engageable by saidarms, said assembly including a metallic shell-like container closed atone end and open at the other end, an electrode member supported ininsulated relation thereto and accessible through the open end of saidshell-like container, said arms being shaped to conform with the contouror said disc-like piezo crystal unit assembly and establish electricalconnection with the shell thereof and engaging the same and a resilientarm supported in insulated relation to said bracket member andestablishing both electrical and mechanical connection with one or theelectrodes of said piezo electric crystal unit assembly.

7. A piezo electric crystal apparatus, comprisingin combination abracketmember having a pair of arms with laterally disposed abutmentsthereon, a piezo electric crystal unit assembly included within ametallic shell-like container closed at one end and open at the otherend, electrode members and a piezo electric plate arranged within saidcontainer, one of said electrode members being supported in insulatedrelation to said shell-like container and accessible through the openend of said shell-like container, said arms being shaped to conform withthe contour of said piezo electric crystal unit assembly and engagingthe same, and a third arm insulatingly mounted with respect to said pairof arms and projectible through the open end or said metallic shell-likecontainer for establishing mechanical and electrical connection with theelectrode accessible through the open end of said metallic shell-likecontainer and maintaining said piezo electric crystal unit assembly indetachable engagement with the laterally disposed abutments on said pairof arms.

8. A piezo electric crystal apparatus, comprising in combination abracket member having a pair of arms with laterally disposed abutmentsthereon, a third arm insulatingly supported with respect to said bracketmember intermediate said pair of arms and resiliently tensioned in thedirection of said pair of arms, a piezo electric crystal unit assemblyincluding a metallic shelllike container closed at one end and open atthe other end, a piezo electric plate and electrode assembly disposedwithin said container, one of the electrodes 0! the electrode assemblybeing insulatingly supported with respect to said container andaccessible through the open end 01 said container, said piezo electriccrystal unit assembly being detachably engaged against the laterallydisposed abutments oi said pair of arms with said third arm projectingthrough the open end of said container and establishing detachableelectrical and mechanical connection with the electrode accessiblethrough the open end of said container.

- 9. A piezo electric crystal apparatus, compris ing in combination asupporting member having a pair oi. arms with laterally disposedabutments thereon extending in a common plane, a third arm insulatinglymounted on said supporting member intermediate said pair of arms andterminating in a contact device, said third arm being tensioned iornormally urging said contact device toward the plane of the laterallydisposed abutments on said pair of arms and a piezo electric crystalunit assembly comprising a metallic shell-like container closed at oneend and open at the other end, a pair of electrodes, a piezo electricplate disposed between said electrodes, one of said electrodes beingresiliently supported with respect to the closed end of said metallicshell-like container and the other of said electrodes being accessiblethrough the open end of said shell-like container, said piezo electriccrystal unit assembly being detachably engaged against the laterallydisposed abutments of said pair of arms when the contact device on saidthird arm is resiliently engageable against the other electrode throughthe open end of said metallic shell-like container.

GEORGE s. WACHTMAN.

